Shot blasting machine



Sept. 21, 1948." w. E. JEWELL 2,449,745

SHOT BLAS TING MACHINE Filed pril 1, 1947 2 Sheets-Sheet 2 INVENTOR.M17256 5. 02/1/ BY b Patented Sept. 21 1948 UNITED snares rum TINGMHCHINE Walter. E..Jewell, LosvA-n gcles; Calif Application April '1,1947; Serial No; 738,5'16' 4iGlaims:

inventionqrelates tolshotr blasting'machines;

and more particularly toa shotib-lasting'ma-chine wherein theworkpieces. are tumble-d While; being exposed: to the stream ofi a.centrifugal shotth -rowingwwheeli Shotblasting is widely: used for-thecleaning of? hard objects -such as ceramics ormetal, and assuch is oftenused ast-hecquivalent: oil sandblasting. or as. a: replacement forsand'eblasting operations; Shot" blasting isparticularlyuseful forcleaning sand; castingszan di forgings; the impactnofi' the shotknocking looseadhering sand particles or scale,- as the casexmay be. Allsurrfaces of the workpieces may: be exposed tothe shotzblast bytumblingvthe workpieces in any con ventional manner as by: placingthem'inside of a rotating drum.

Prion shotr blasting" machines hav generally employeclz a stream of airfoncarrying the shot torthe objects to be blast'ed. Machines emplow ing.airb-last's accordingly may include a=plurality of: moyableon fixed"nozzleswhi'ch can be directed from. a .varietyrof: angles towards iworkpieces: that are:v generally carried on a conveyor belt or-may bedisposed upon a. rotatablev fixture; Also stream of shot fon shotblasting have been ob"- tainect. from: rotating wheels having paddlesorblades thereon that could centrifugally throw shot that is fedtowardsthe centenofthewheel from; any convenient. source; such'as achute. These centrifugal; wheels are more efficient than the: airblasts. ofshot, and' employa mucl'tmore simple. mechanism thanthatrequired forair blasts.

While ;severali attemptsthave been made to -combine: centnifugalshot-throwing wheel's withltumblers so-that allisurfacesofi theworkpiecesmay be exposedato the shotblast, these in-general have not:been successful. The principal -difficultyhas apparently been. due tothe: fact that no suitable mechanism: on device could=be obtained fordi-- recting the shot into the tumbl'er. Forexampl'e; tumblers have.been. formed of drums mounted for rotation. upon a. generally inclinedor verti-- calaxis; and the workpieces tumbled in the.-

drums. have been; exposed to, the: blast. of shot by having one end ofthe drum 011811.: These strum tures, however, are. not. particularlysatisfactory;

since only a smallquantity. of tumbled efliciently atonetimework-pieceslmay be invention, seeks. to overcome these. defects.v

ofiprion shot blasting machinles by providing tumbias for workpiecesthat may include rotatable drums mountedon. generally horizontal axes sotheta large tumbling. capacity be obtained.

Further; instead ofi: opening' one" and off the drum so'ethats. anoutside source of-ishoi'. ..may be utilized; Lhaveprovidediashot-throwing mechanism; that marcbe disposedwithinlth e tumbler itself;Inesmuchra-st-suchi shotv blasting mechanism-s am'particularly: bulky.and:v would. interfere with the mounting of a, drum that is supportedupon a shaf-il;.lI have arrangedumy: tumbling drum-so that vitamay besupported :at" its p-eriphery only upon driving rollers. H'I hisastructure also-per mits the utilization of an extremely largechargingyidoor: for; the drum which: door may be situated at the. end;of the: drumiopposite from: that inrwhich. the shoteth'rowing. device isdisposed;

Thee in'senti-ona on 8;: shotsthrowing dcviceinto the interior of atumbling drum raises the asd'cled problem; of; adequately covering;theentire axial lflngt-lh ofrthe: :drumrzwitln the shot blast so as toobtain a uniform and efficient blasting of the tumbledi workpieces.While ibwl'S theoretically possible; tmaligm an elongatedicshot-throwingwheel. with; the'raxis ofzithedrum and" to throw shot fromtheientinelengthz ofit-he Wheel so as to cover: thez entine axiah lengthz of lthedrum, this structurezisinot practical; at. present. My invention',howeyen, includes. means for employing a simplea-shot-throwinge wheelhaving: a relatively thin: widthitoi the radiali shot -throwing patternin suchta manner that; the. entireaxial lengthof. the drumvwillz be:adequatelysblasteds This structure may. include. earshot-throwing wheelhavihgits axis; oitrotationat "an." angle to the axis of rotati'onofi1the drum,- and when the wheel is" dis posed on? the interiorof" thedrum; it will direct a shot pattern generally aligned with the diagonalcorners of the drum;

in; ordinary tumbling operations, the workpiecespreferably cover only"the." bottom portion of the tumbled drumsc that. all surfaces of theworkpieces may be. exposedjtm ashot blast with the fewest number ofrotations. Accordingly; therefore, the shotrthrowingwheel must. be(ilesigned. to. deliver. shot onlyloverz-that part of the. interiorsurface? of.. the .;drum: occupied; by the; workpieces; inasmuch as anyshotthat is directed. towards parts of the drum not covered bytheworkpieces will; quickly erode away the drum and render itunserviceable: My. inventionaccordingly: includes: an improved:shot-throwing wheel: structure having a very; directive shot pattern sothat the life; of the drum will. be greatly extended. l

It. is a: principal objectroi my. invention to-prowide an. improved:shoti blasting machine wherein an improved shot-throwing device for.shot blast-.

ing machines.

Other objects and advantages of my invention will be apparent in thefollowing description and claims, considered together with the accompanying drawings, in which Fig. 1 is an elevation front View of a shotblastother things, the mechanism for delivering shot from the bottom ofthe machine to the top of :the

machine; l y

Fig.3 is-a sectional view along the-line III-III ofv Fig. l'showing thelocation and relative dis-- position ofthe shot-throwing wheel and thetumblingdrum; l

r Fig. 4 is a sectional view through the tumbling drum taken alongthe'line IVIV of Fig. 3;

Fig. 5 is an elevation view of one side of the shot-throwing wheelastaken along the line VV Fig. 6 is a sectional view through theshotthrowing wheel as taken along the line VI-VI of Fig. 5; and

Fig. 7 is a sectional view through a chilled surface type ofwmold forcasting the shot-throwing blades of the shot-throwing wheel of Fig. 5.

While my invention may be embodied in apparatus comprising essentially adrum, shotthrowing wheel,. and means for feeding shot to theshot-throwing wheel, I prefer to add refinements thereto that increasethe utility and efficiency of my shot blasting machine. Accordingly,referring to Figs. 1, 2, and 3, a shot blasting machine [B may include arectangular frameworkl l formed of angle irons or other structuralshapes of great strength. The entire rectangular frame. H may beenclosed with sheet metall2 so as to form a dust proof case about theshot blasting machine, and the dust may be removed by any suitablemechanism, for example by a suction exhaust pipe I3. A suitable door inthe sheet metal case l2 may be provided forpermitting access to thetumbling drum.

The tumbling drum may be in the form of a steel cylinder l4 having aplurality of perforations 16 in the cylindrical wall thereof. The drummay be'mounted for rotation on, and may be driven by, a plurality offlanged driver wheels l1, and each end of the drum l'4 may be providedwith heavy steel tires 18 for engagement with these drivers l1.

,The drivers I! may be mounted upon two shafts I9 generally parallel tothe axis of the drum l4, and these shafts may be journaled 'in suitablebearings 2| mounted upon horizontal portions of the frame I, I.- Theseshafts -l9 may-project from the rear of the sheet metal dust case [2 fora driving engagement by a geartrain driven by a motor 22 which ispreferably electric. .A suitable reduction in speed between the motor 22and the drum [4 must be obtained inasmuch as the rotation of the drum ispreferably on the order of about 1 R. P, M. Accordingly a small sprocket23 on the motor 22 may engage a large sprocket 24 secured to a reductiongear box 26 from which may lead suitable belts or chains having adriving engagement with one of the shafts 19. The two shafts l9 may beinterconnected by a belt or chain drive 21 so that all four wheels I!will drive the drum l4.

The drum l4 may be charged with workpieces by means of a large chargingdoor 28 hingedin any suitable manner, as by a rod 29, to the drumitself. An inspection door 31 may be provided in this charging door ifdesired. Accordingly the door 23 may be opened and workpieces placedwithin the drum l4 and the door 28 may then be closed and securelylocked. Thereafter the drum will be rotated and the workpieces will tendto rotate with'the drum until they reacha point on 4 their upward travelwhere the forces of gravitywil-l cause them to roll down over the .pileof workpieces within the drum and thus give rise to the tumbling action.The shot with which the-workpieces are blasted, and the blastedparticles of sand, scale, or other coating may fall through the smallholes ['6 into a hopper 32. The shot may roll from the hopper 32 intothebottom part 33a of an elevator shaft 33 so that the .bottom part 33aof the shaft acts as abin for the shot. If desired, an air'inlet openingmay be formed adjacent the bin portion 33a, of the elevator. shaft 33 sothat air-will be sucked upwardly within the'dust casing l2 to theexhaust pipe I3 and thereby clean the shot of scale and line particles.The shot-throwing mechanism is shown in general in Fig. 3, and has asits essential part a shot-throwing wheel 4| which will be described inmore detail. with referenceto Figs. 4 through 7, inclusive. zThe wheel4| may be mounted'upon a generally horizontal shaft 34 journaled inbearings 35. The shaft may be driven by an electric motor 36.mountedupon aplatform 31 disposed atthe rear of the shot blasting machine Ill.A drive may be effected between the motor 36 and the shaft 34 by anysuitable device such as pulleys and; one or more belts or chains 38.

.Also it will be noted that-the rear end of the drum 14 may be centrallyrelieved so that only an annular end portion l4a remains. Project-4 inginto the central opening formed by the annular end plate l4a, may be agenerally tubular member42 to which the inner bearing 35 is secured, andthis tubular member may be secured in turn to upright portions of theframe I l. The horizontal shaft-34 may be located generally in the samehorizontaliplane that includes the axis of the rotatable drum 14, butvariations of smallv amounts may be made therein as will be apparent tothose skilled in the art.

Shot maybe supplied to the throwing wheel 4i by. means of .a continuoussupply mechanism disposed within the elevator shaft 33. For example,

an endless belt maybe employed for'this purpose having buckets securedthereto as shown in Fig. 2; Accordingly pulleys 43 may be journaled inthe bottom and top of the'elevator shaft'33, and an endless belt 44 maybe passed about the pulleys and may have buckets 46 secured theretowhich will dip into a'pile of shot 4'! formed in the bin portion 33a-of"the shaft 33. The upper pulley 43' may bedriven' by any suitablemechar'iisni' suchas a sprocket 48"co'nnected by a chain 49 to 5sprocket, 51:- mounted on a1 crosss'shafti having avlargeipulley 52.driven; by; an electric. motor: 53.

the endless :belt. moves. about. pulleys;v it

will? pick up shot: at, the bottom. of. the; shaft 33 and. deliver;it-at the: top'ofs the shaft to: 3.151111 ableisupply mechanism such asan tube 54 (Fig.

4!) leading from the top: of the. elevatorgshaft to the;sho-t'l-throwinga wheel M. The: rate; of. supply of sh'ot torthecentrifugal. wheel. 4 I maybe. .reguelatecli by placing? a. slidingplate; 3-llr or: similar mechanism between the hopper 32 and thfi botrtomw33a' of. theelevator" shaft 33... l

- The construction of theshot-throwingwheel 41-- mayrbe best explained:with=reference1to Figs.

31.4 ,5; and- 6. Referring to Fig. 3, it willibe: noted that/ia.relatively thick and: heavy wear plate 5.6 may be. secured: to: theendgofi the tubular projectiom 42;. and? the shot supply tube 54-- maypass through an opening in thiswea-r plate to. deliver shot-t'oflthewheel 41. Apertured square plates 51: may be'spacedifrom the end of. thetubular portion 42 to trap shot that t'end's-to ride along the shaft 34to the outside: of the machine. The wheel; may include anxannular hub581 resting upon: a 'shoulder on the end of the shaft and a grooved:plate: 59 may be secured against the hub 58 by a washer 6:! and remitv62-. Blades: 63. may be secured to-the circular plate 59 and may bepartially disposed withinthe grooves of the. plate 59. r

The detailed construction of the centrifugal WheelJH is best illustratedin Figs. 5' and 6; whereinlit will beinoted that. the blades G3 mayinclude a: generally channel-shaped: member '64: having a ribbedtransverse boss 96 integrally formed thereon. One'edge ofthechannelshape may be disposed withintliegrooves of the plate 5.9, whichgrooves may be'designated as 59a. A bolt 61- may pass through thetransverse boss Strand. through the plate 59" to securely fastenthenblades 63" to the circular plate: 59f The pl'ate59 isdesignedt'orotate at a high rate-of speed, for example 2 000 R. P. M., and: as theshotxrolls.outwardly on the blades 63* they bear thereagainst veryheavily due to the increased angular acceleration- Whilethe balls moveoutwardly with some rolling action, there is also a considerable slidingaction, and the blades 6-3 are accordingly subject toistrong forces thattend to wear the blades.

Accordingly I prepare the blades 63' to accommodate these Wearingtendencies, and I have found that a chill casting of the wear surfaceperforms quite-satisfactorily when the blades 63 are formed from highcarbon iron. This casting technique is illustrated in Fig. 7,.wherein amold mayinclude asandporti'on 68 for the main body of the-blades 63; butthe portion of the mold. forming the channel' of the blades may beformed of a metal as at.69.z Therefore if a high carbon ironalloy isused, for example cast-iron, the surface of the channel will be chilledduring this casting operation due to the high thermal conductivity ofthe metal portion 68 of the mold. This chilling action will cause analignment of metal grains perpendicular to the channel that give rise togreat wear resistance.

The operation of the mechanism may be initiated by opening the chargindoor 28 and inserting therein any material that is to be shot blasted.For example, a tumbling drum approximately four feet in diameter andabout three feet in axial length may be loaded with eight hundred to twothousand pounds of metal objects, and the door 28 may then be closed andsecurely locked. A supply of hard steel shot may be disposedlinz the:bott om of the elevator. shaft; 33 until ax. substantial pile isaformedas indicated at 4:1 (Fig. 29;, The: drum rotating motor 22 may them bestarted; the.shot thro wingm otor-3flfimay then be started; andl theelevator motor- H may nextsbe started: Also a suitable exhaust fan maybe omrated to Withdraw air from the exhaust 'staclr: I53 (Fig: ll); Theendless belt' M there after continuously moves on the pulleys-43 andther buckets E6 on the beltd'cliver-"shotto the top of the elevatorshaft 33. whereupon-the shot is dumped into the delivery pipe 54;Thed'eliveryi pipe- 51! passes through the wearplate 56 (Fig. 30 anddeliversshot totherapidlywhirling wheel d ll The blades- 63 of thiswheel'take the shot which is delivere'd at their most inward end and:give it a: very rapid angular acceleration-dhe tothe highrateofrot'ation ofthe wheel ll-which may be-aof the order of 2 :000R. P:Thisamgular acceleration gives-riseto' a radial -m'ovement of theshot,causing the shot to skid or roll along the channel= portions of theblades 63 until they are delivered with-a tangential trajectory to theinterior of' the drumfl M The angular spread of the tangentialtrajectory may beadiusteol by any suitable means to substantially thatshown by arrowsl llfiinlFig. 44 The. chargewithinthe drum M which isslowly rotating will occupysubstantially this angular portion of theinterior of 'th'e drum l4, an'd accordinglywill be blastedibythe shotwith verylittle o'f the shot-striking theidrum interior itself-of thedrum: l t? The spent shot; together with the" particles knocked offdueto the impact with the work: pieces, will pass through the' holes: F6i-n the drum to be collectedby the hopper: 3-2: Any suitable mechanism(notxshowm may beutilize'd for separating the blasted' material fromther's-hoi'i; which shotmay-then be re-usedi for a great cycles. This recycling of the shotoccunsit I OuS fI'Ol'l'L the hopper-32: down intethelower end of the elevator shaft 33 to formtheshot pile 47'. Theoperation-is continuousfor'any dcsired! length. ofti me; and: the usualblasting times are from: filve to twenty minutes, depending upon the:type. of. material: being clean'ed or treated; When. its is desired;tobremove the. chargerat, the end. of the. run, the. motors. are turnedolii the charging doorwzlli opened and the material removed from thedrum it which may beeasi'ly affected,, for. example by. raking: .the:matenial from thedrum-intio a waiting= truck orother receptacle; Theoperation of. the machinemay be entirely,

dust freedue to the enclosure-of the drum Mlby the case l2, togethenwiththe exhausting operation performed by the stack. 11:3... The machineaccordinglymaybe placed in any type of; shop without interfiering withnearby, operations reiquiring substantial freedom firomdustand grit-1..

By referringto Eig. 3; itwill'be noted: that the shot-throwing Wheel 4|is disposed at an angle to the axis of the drum M. Also by referring toFig. 4 it will be noted that the angle between the shot-throwing limits10 is such that the shot will be delivered from one corner of the drumand diagonally across the drum to the other corner. Thus all portions ofthe workpieces within the drum will be treated simultaneously. At onecorner of the drum the pieces on the highest end of the constantlytumbling pile of workpieces will be treated, and the line of shot willtraverse the pile until at the other diagonal corner of the drum thelower end of the tumbled pile will be blasted. As noted in Fig. 4, therelation of the feed tube 54 with respect to the centrifugal wheel 41 issuch that the drum M should be rotated in an opposite directionto'obtain proper coverage.

Hard steel shot is preferred as the blasting medium, and the wheel 4|may ive this a velocity sufficient so that the shot is able to penetratea WOOdGIl board, but not excessive so that it will mar the charge-beingcleaned. The positioning of the shot-throwing mechanism directly withinthe tumbling drum gives the most direct contact of the shot-with theworkpieces, and makes possible very close control of shot velocity withrespect to the charge being treated. In this connection I have foundthat shot-throwing wheels employing two blades are greatly superior tothose having a greater number ofblades insofar as delivering a clean anddirect shot pattern is concerned. This positioning of the shot throwerwithin the tumbler is made possibleby mounting of and rotation of thedrum upon driving wheels rather than by an axial shaft.

The drum I4 is preferably formed of heavy steel such as one-half inchsteel, and the holes l6 therein may be drilled or punched. The heavytires I8 which engage the driving wheels I! may be made withconsiderable accuracy compared to the drum itself. In this connection itshould be noted that the drum may be made of plates Welded together intoa general cylindrical shape, or may be formedof one or more sheetsrolled into a circular cylindrical shape. The drivers I! are preferablyformed of very hard material such as chilled cast-iron. The moving partsare relatively few in number and when made with extreme ruggedness thefinal machine is free of operational breakdowns and the only substantialmaintenance operation thereupon need be the replacement of the blades 63on the centrifugal Wheel 4|, Further, the shot-throwing wheel is soconstructed as to handle blasting particles other than shot. Forexample, the conventional grits often used in place of round shot may beemployed.

While I'haVe described my invention with respect to a particularembodiment thereof, I do not limit myself to this embodiment, since itis obvious that various modifications could be made therein withoutdeparting from the true spirit and scope of the invention. Accordingly Ilimit m invention only by the terms of the following claims.

I claim:

1.- A shot blasting machine comprising a rotatable tumbling drum havinga generally horizontal axis, a generally horizontal rotatable shaftprojecting into the drum at one end thereof and at an acute angle to thedrum axis, and a narrow shot-throwing wheel disposed on the shaft insideof the drum so that a shot pattern may be thrown diagonall across thedrum to cover the entire axial length of the drum.

2. A shot blasting machine comprising a rotatable tumbling drum having agenerally horizontal axis, a generally horizontal rotatable shaftprojecting into the drum at one end thereof and at an acute angle to thedrum axis, a narrow shotthrowing wheel secured tothe shaft insideofthedrum and characterized by having two shotthrowing blades, and means forsupplying shot to the shot-throwing wheel 'sothat a shot pattern may bethrown that coversthe entire axial length of the drum but at an angle tothe axis of the drum.

3. A shot blasting machine comprising a rotatable tumbling drum having agenerally horizontal axis, a generally horizontal rotatable shaftprojecting into the drum at one end and at an acute angle to the drumaxis, a narrow shot-throwing wheel disposed on the shaft inside of thedrum, rotatable wheelscontacting the outer periphery of the drum forsupporting and rotating the drum, means for supplying shot to theshot-throwing wheel, and a large charging door disposed in the other endof the drum.

4. A shot blasting machin comprising a framework, at least fourrotatable Wheels mounted within the framework, means for driving atleast one of the wheels, a perforated drum disposed on the wheels andhaving a generally horizontal axis, a generally horizontal rotatableshaft projecting into the interior of the drum through one end thereof,means for rotating the shaft at a high rate of speed, a shot-throwingwheel disposed upon the shaft within the drum for throwing a pattern ofshot diagonally across the drum, a hopper disposed below the drum forreceiving shot that-falls through the perforations of the drum, adust-tight case secured to the frame about the drum and connected to thehopper, an elevator secured to the framework for lifting shot from thebottom of the hopper to a point abovethe shot throwing wheel, a chuteconnecting the top of the elevator with the shot-throwing wheel, andmeans for passing air through the hopper and the dust-tight case,whereby foreign particles and dust may be removed from the shot and fromthe dust-tight case, WALTER E. JEWELL.

REFERENCES CITED The following references are of recordin the file ofthis patent:

UNITED STATES PATENTS Date

